WO2023171728A1 - Sensor device - Google Patents

Abstract

This sensor device comprises, on a support body, a functional layer and a pair of electrodes that are connected in series with the functional layer interposed therebetween. The pair of electrodes are constituted by: a first electrode having a temperature coefficient resistance with one of a positive value and a negative value; and a second electrode having a temperature coefficient resistance with the other of the positive value and the negative value.

Description

sensor device

The present invention relates to a sensor device.

A sensor device comprising a pair of electrodes on a substrate with a functional layer interposed therebetween is used, for example, in electronic equipment such as sensors such as pressure sensors and acceleration sensors, high frequency filter devices, and piezoelectric actuators.

As such a sensor device, for example, a first electrode layer, a piezoelectric thin film mainly composed of a piezoelectric material, and a first electrode layer are formed on a thin polymer film mainly composed of a polymer compound obtained by polymerizing monomers. A piezoelectric element in which two electrode layers are formed is disclosed (for example, see Patent Document 1).

In the piezoelectric element of Patent Document 1, the first electrode layer and the second electrode layer are made of, for example, tin, aluminum, nickel, platinum, gold, silver, copper, chromium, iron, magnesium, molybdenum, niobium, tantalum, titanium. , zinc, zirconium, tungsten, palladium, rhodium, iridium, rubidium, titanium nitride, chromium nitride, and molybdenum disilicide.

Japanese Patent No. 5136973

However, in the piezoelectric element of Patent Document 1, the electrical resistance of the first electrode layer and the second electrode layer varies depending on the temperature change of the environment in which it is used, so that the voltage of the first electrode layer and the second electrode layer changes. Since the drop varied, there was a problem in that the output varied depending on the temperature of the environment.

An object of one aspect of the present invention is to provide a sensor device that can suppress fluctuations in the voltage drop of an electrode caused by temperature changes in the environment in which it is used.

One embodiment of the sensor device according to the present invention includes, on a support, a functional layer and a pair of electrodes connected in series via the functional layer, and the pair of electrodes has a positive value and a negative value. The first electrode has a temperature coefficient of resistance of one of the positive and negative values, and the second electrode has a temperature coefficient of resistance of the other of a positive value and a negative value.

One embodiment of the sensor device according to the present invention can suppress fluctuations in the voltage drop of the electrodes caused by temperature changes in the environment in which the sensor device is used.

1 is a perspective view showing the configuration of a sensor device according to an embodiment of the present invention. FIG. 1 is a schematic cross-sectional view showing the configuration of a sensor device. It is a perspective view showing an example of other composition of a sensor device. FIG. 7 is a plan view showing an example of another configuration of the sensor device.

Hereinafter, embodiments of the present invention will be described in detail. In order to facilitate understanding of the explanation, the same components in each drawing are denoted by the same reference numerals, and redundant explanation will be omitted. Further, the scale of each member in the drawings may differ from the actual scale. In this specification, "~" indicating a numerical range means that the lower limit and upper limit include the numerical values written before and after it, unless otherwise specified.

[Sensor device]
The sensor device according to the present embodiment includes, on a support, a functional layer and a pair of electrodes connected in series via the functional layer, and the pair of electrodes has one of a positive value and a negative value. a first electrode having a temperature coefficient of resistance (TCR) of a value of , and a second electrode having a TCR of the other of a positive value and a negative value. In this embodiment, the sensor device is a laminate including a support, a functional layer, and a pair of electrodes connected in series via the functional layer, the support is a flexible base material, and the functional layer A case where is a piezoelectric layer will be explained. Note that the functional layer is not limited to a piezoelectric layer, but may also be a temperature measurement layer, a strain detection layer, or the like.

FIG. 1 is a schematic cross-sectional view showing the configuration of a sensor device according to this embodiment. As shown in FIG. 1, the sensor device 1A includes a flexible base material 10 as a support, a first electrode 20, a piezoelectric layer 30 as a functional layer, and a second electrode 40 on a flexible base material. They are stacked in this order from the 10th side. The sensor device 1A can be formed into any shape such as a sheet (film).

In this specification, the thickness direction (vertical direction) of the sensor device 1A is defined as the Z-axis direction, and the lateral direction (horizontal direction) orthogonal to the thickness direction is defined as the X-axis direction. The second electrode 40 side in the Z-axis direction is the +Z-axis direction, and the flexible base material 10 side is the -Z-axis direction. In the following description, for convenience of explanation, the +Z-axis direction will be referred to as upper or upper, and the -Z-axis direction will be referred to as lower or lower, but this does not represent a universal vertical relationship.

(Flexible base material)
The flexible base material 10 is a substrate on which the first electrode 20 is installed, and has flexibility so as to provide flexibility to the sensor device 1A. Any material can be used as the flexible base material 10, such as a plastic base material, a silicon (Si) substrate, a metal plate, a glass base material, etc.

When using a plastic base material, it is preferable to use a flexible material that can provide flexibility to the sensor device 1A.

As the material forming the plastic base material, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylic resin, cycloolefin polymer, polyimide (PI), etc. can be used.

The flexible base material 10 may be transparent, translucent, or opaque. Note that transparent refers to having transparency to visible light (light with a wavelength of 380 to 780 nm) to the extent that the inside of the flexible base material 10 can be visually recognized from the outside, and the light transmittance of visible light is It is 40% or more, preferably 80% or more, and more preferably 90% or more. The light transmittance is measured using "Plastics - How to determine total light transmittance and total light reflectance" specified in JIS K 7375:2008.

When light transmittance is required for the sensor device 1A, it is preferable to use PET, PEN, PC, acrylic resin, cycloolefin polymer, etc. These materials are suitably used when the electrode used in the sensor device 1A is a transparent electrode. Further, in cases where the sensor device 1A does not require optical transparency, such as healthcare products such as pulse rate monitors and heart rate monitors, and in-vehicle pressure sensing sheets, the above-mentioned materials, translucent or opaque plastic materials may be used.

For example, aluminum, copper, stainless steel, tantalum, etc. can be used as the material for forming the metal plate.

The thickness of the flexible base material 10 is not particularly limited, and can be any thickness depending on the use of the sensor device 1A, the material of the flexible base material 10, etc., and may be, for example, 1 μm to 250 μm. . Note that the method for measuring the thickness of the flexible base material 10 is not particularly limited, and any measuring method can be used.

Note that in this specification, the thickness of the flexible base material 10 refers to the length in the direction perpendicular to the main surface of the flexible base material 10. The thickness of the flexible base material 10 may be, for example, the thickness measured at an arbitrary location in the cross section of the flexible base material 10, or may be measured at several arbitrary locations and the measured values It is also possible to take the average value. Hereinafter, the definition of thickness will be similarly defined for other members.

(first electrode)
The first electrode 20 is provided on the upper main surface (upper surface) of the flexible base material 10. The first electrodes 20 may be formed in a thin film shape on a part or the entire surface of the flexible base material 10, or may be provided in plural in parallel in a stripe shape. Note that when the flexible base material 10 has conductivity such as a metal plate, the first electrode 20 may not be provided because the flexible base material 10 can also function as an electrode.

The first electrode 20 can be made of any conductive material. The materials include Pt, Au, Ag, Cu, Mg, Al, Si, Ti, Cr, Fe, Ni, Zn, Rb, Zr, Nb, Mo, Rh, Pd, Ru, Sn, Ir, Ta, and W. Metal oxides such as zinc oxide, tin oxide, copper oxide, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), IZTO (Indium Zinc Tin Oxide), IGZO (Indium Gallium Zinc Oxide), titanium nitride Nitrides such as (TiN) chromium nitride (CrN) and tantalum nitride (TaN), and carbides such as silicon carbide (SiC) can be used. When light transmittance is required, an oxide conductive film made of a metal oxide such as ITO, IZO, IZTO, IGZO, etc. can be used as the material. If light transparency is not essential, metal or the like may be used.

From the viewpoint of suppressing the unevenness of the interface between the first electrode 20 and the piezoelectric layer 30 and the grain boundaries, the first electrode 20 may be an amorphous film. By forming an amorphous film, it is possible to suppress unevenness on the surface of the first electrode 20 and generation of crystal grain boundaries that cause leakage paths. Further, the upper piezoelectric layer 30 can be grown with good crystal orientation without being affected by the crystal orientation of the first electrode 20.

The thickness of the first electrode 20 can be designed as appropriate, and is preferably 3 nm to 100 nm, for example. If the thickness of the first electrode 20 is within the above preferable range, it can function as an electrode and the sensor device 1A can be made thinner.

The first electrode 20 has a TCR of one of a positive value and a negative value. The TCR of the first electrode 20 may have a value with a different sign from the TCR of the second electrode 40, and the TCR of one of the first electrode 20 and the second electrode 40 is a positive value. The TCR of the other electrode is negative.

Note that TCR is one of the temperature characteristics of the first electrode 20 and the second electrode 40, and depends exclusively on the materials that constitute the first electrode 20 and the second electrode 40. The TCR of the first electrode 20 and the second electrode 40 depends on the type of material that constitutes the first electrode 20 and the second electrode 40, the thickness of the first electrode 20 and the second electrode 40, the first When the electrode 20 and the second electrode 40 are made of a composite material containing a plurality of materials, they can be set to exhibit metallic behavior or semiconductor-like behavior depending on the content of each material. When TCR is a positive value, the first electrode 20 and the second electrode 40 exhibit metallic behavior, and when TCR is a negative value, the first electrode 20 and the second electrode 40 exhibit metallic behavior. exhibits semiconductor-like behavior.

The details of the relationship between the TCR of the first electrode 20 and the TCR of the second electrode 40 will be described later.

(Piezoelectric layer)
The piezoelectric layer 30 is provided on the main surface (upper surface) above the first electrode 20. The piezoelectric layer 30 preferably contains an inorganic material as a main component.

Note that the main component means that the content of the inorganic material is 95 atm% or more, preferably 98 atm% or more, and more preferably 99 atm% or more.

As the inorganic material, a piezoelectric material having a perovskite crystal structure, a piezoelectric material having a wurtzite crystal structure (wurtzite crystal material), etc. can be used. Note that in this embodiment, since the piezoelectric layer 30 is used as the functional layer, a piezoelectric material having a perovskite crystal structure, a wurtzite crystal material, etc. are used, but when the functional layer is other than the piezoelectric layer 30, Depending on the type of functional layer, metals such as Pt, Au, Ag, Cu, Mg, Al, Si, Ti, Cr, Fe, Ni, Nb, Mo, Ru, Sn, and Ta may be used.

The wurtzite crystal structure is represented by the general formula AB (A is a positive element and B is a negative element). A wurtzite crystal material has a hexagonal unit cell and has a polarization vector in a direction parallel to the c-axis.

As the wurtzite crystal material, it is preferable to use a material that exhibits piezoelectric properties of a certain value or more and that can be crystallized in a low-temperature process of 200° C. or less. The wurtzite crystal material contains at least Zn among Zn, Al, Ga, Cd, and Si as the positive element A represented by the general formula AB. As the wurtzite crystal material, for example, zinc oxide (ZnO), zinc sulfide (ZnS), zinc selenide (ZnSe), zinc telluride (ZnTe), etc. can be used. Among these, ZnO is preferred as the wurtzite crystal material since it can be relatively well oriented in the c-axis even in a low temperature process. These may be used alone or in combination of two or more. When two or more types of wurtzite crystal materials are used in combination, one or more of these components may be included as a main component, and other components may be included as optional components.

In addition to Zn, the positive element A may contain at least one of Al, Ga, Cd, and Si. As these wurtzite crystal materials, for example, aluminum nitride (AlN), gallium nitride (GaN), cadmium selenide (CdSe), cadmium telluride (CdTe), silicon carbide (SiC), etc. can be used.

The wurtzite crystal material preferably contains ZnO and consists essentially of ZnO, and more preferably consists only of ZnO. "Substantially" means that in addition to ZnO, unavoidable impurities that may be unavoidably included during the manufacturing process may be included.

In addition to the above-mentioned ZnO, ZnS, ZnSe, and ZnTe, the wurtzite type crystal materials include alkaline earth metals such as Mg, Ca, and Sr, or vanadium (V), titanium (Ti), zirconium (Zr), and silica. (Si), lithium (Li), and other metals may be included in a proportion within a predetermined range. These components may be contained in an elemental state or in an oxide state.

In addition to the main component, the piezoelectric layer 30 may include at least one of Ar, Kr, Xe, and Rn as an additive element.

The content of the additive element in the piezoelectric layer 30 is not particularly limited, and may be within a range that allows the piezoelectric layer 30 to have a wurtzite crystal structure.

The method for measuring the content of the additive element contained in the piezoelectric layer 30 is not particularly limited as long as it is a measurable method. The content of the additive elements contained in the piezoelectric layer 30 may be measured, for example, by Rutherford backscattering spectroscopy (RBS) using Pelletron 3SDH (manufactured by NEC Corporation) as a measurement device, or by measuring secondary ion It may be measured by mass spectrometry using dynamic SIMS (D-SIMS) or the like.

The thickness of the piezoelectric layer 30 is not particularly limited, and it has sufficient piezoelectric properties, that is, polarization properties proportional to pressure, and reduces the occurrence of cracks in the piezoelectric layer 30 to prevent leakage paths between electrodes. Any thickness is sufficient as long as it can suppress this and exhibit piezoelectric properties stably. The thickness of the piezoelectric layer 30 may be, for example, 5 μm or less.

The film density of the piezoelectric layer 30 is not particularly limited and can be designed as appropriate, as long as it is within a range that can improve the crystal orientation of the piezoelectric layer 30 and suppress an increase in film stress. Note that the method for measuring the film density is not particularly limited, and for example, X-ray reflectance measurement (XRR) or the like can be used.

The crystal orientation of the piezoelectric layer 30 is indicated by the full width at half maximum (FWHM) obtained when the surface of the piezoelectric layer 30 is measured using an X-ray rocking curve (XRC) method. It will be done. That is, the crystal orientation of the piezoelectric layer 30 is determined by the peak of the rocking curve obtained when diffraction from the (0002) plane of the crystal of the piezoelectric material contained as a main component in the piezoelectric layer 30 is measured by the XRC method. It is represented by the FWHM of the waveform. Since the piezoelectric material included in the piezoelectric layer 30 has a wurtzite crystal structure such as ZnO, FWHM indicates the degree of parallelism of the c-axis direction alignment of the crystals forming the piezoelectric material. Therefore, the FWHM of the peak waveform of the rocking curve obtained by the XRC method can be used as an index of the c-axis orientation of the piezoelectric layer 30. Therefore, it can be evaluated that the smaller the FWHM of the rocking curve, the better the crystal orientation of the piezoelectric layer 30 in the c-axis direction.

In addition, the crystal orientation of the piezoelectric layer 30 can be determined by the FWHM of a rocking curve obtained by measuring the diffraction from the (0002) plane of the ZnO crystal included as a piezoelectric material in the piezoelectric layer 30 by the XRC method. , the peak intensity can also be evaluated. That is, the crystal orientation of the piezoelectric layer 30 can also be evaluated using a value obtained by dividing the integral value of the peak intensity by FWHM as an evaluation value. In this case, it can be evaluated that the stronger the peak intensity of the rocking curve and the smaller the FWHM, the better the c-axis orientation of ZnO. Therefore, the larger the evaluation value obtained by dividing the integral value of the peak intensity by the FWHM, the better the crystal orientation of the piezoelectric layer 30 can be evaluated.

When two or more types of wurtzite crystal materials are used together, the piezoelectric layer 30 may be constructed by laminating piezoelectric layers made of the respective wurtzite crystal materials.

(Second electrode)
As shown in FIG. 1, the second electrode 40 is provided on the upper principal surface (upper surface) of the piezoelectric layer 30 and is arranged to face the first electrode 20. The second electrode 40 can be formed of any conductive material, and the same material as the first electrode 20 can be used. When the sensor device 1A requires light transparency, the second electrode 40 may be a transparent oxide conductive film such as ITO, IZO, IZTO, IGZO, or the like. When optical transparency is not essential, the second electrode 40 may be a metal electrode of a good conductor such as Au, Pt, Ag, Ti, Al, Mo, Ru, Cu, or the like.

Similarly to the first electrode 20, the second electrode 40 may be formed in the form of a thin film on a part or the entire surface of the piezoelectric layer 30, or may be formed in any shape as appropriate. For example, when a plurality of first electrodes 20 are provided in parallel in a stripe shape, the second electrodes 40 are arranged in a direction perpendicular to the direction in which the stripes of the first electrodes 20 extend in plan view. , a plurality of stripes may be provided in parallel.

The thickness of the second electrode 40 can be designed as appropriate, and is preferably 20 nm to 100 nm, for example. If the thickness of the second electrode 40 is within the above-mentioned preferable range, it can function as an electrode and the sensor device 1A can be made thinner.

The second electrode 40 has a TCR with a different sign than the first electrode 20. The TCR of the second electrode 40 may have a different sign from the TCR of the first electrode 20, and when the TCR of the first electrode 20 has a positive value, the TCR of the second electrode 40 has a negative value. When the TCR of the first electrode 20 is a negative value, the TCR of the second electrode 40 is a positive value. The sign, size, etc. of the TCR of the second electrode 40 can be set in the same way as for the first electrode 20, so details will be omitted.

The first electrode 20 and the second electrode 40 have TCR values of different signs, so that the TCR between the electrodes is canceled out, but the temperature change in the resistance of the first electrode 20 and the second electrode 40 It is preferable that the ratio of
|(ρ ₁ /t ₁ ×α ₁ )+(ρ ₂ /t ₂ ×α ₂ )|<2×min(|ρ ₁ /t ₁ ×α ₁ |,|ρ ₂ /t ₂ ×α ₂ |) ...(1)
(In the formula, ρ ₁ is the electrical resistivity (unit: Ω・m) of the first electrode 20, t ₁ is the thickness (unit: m) of the first electrode 20, and α ₁ is ρ 2 is the resistance temperature coefficient (unit: %/K) of the first electrode 20, ρ ₂ is the electrical resistivity (unit: Ω·m) of the second electrode 40, and t ₂ is the resistance temperature coefficient (unit: %/K) of the second electrode 40. (unit: m), and _α2 represents the resistance temperature coefficient (unit: %/K) of the second electrode 40.)

The ratio of the resistance of the first electrode 20 to temperature change expressed as (ρ ₁ /t ₁ ×α ₁ ) and the ratio of the resistance of the second electrode 40 expressed as (ρ ₂ /t ₂ ×α ₂ ) The sign of the ratio to the temperature change exists only in the sign of the TCR of the first electrode 20 and the second electrode 40, and does not change otherwise. Therefore, if the signs of the TCR of the first electrode 20 and the second electrode 40 are positive or negative and opposite, the resistance of the first electrode 20 expressed as (ρ ₁ /t ₁ ×α ₁ ) The sign of the ratio to the temperature change and the sign of the ratio of the resistance of the second electrode 40 to the temperature change, expressed as (ρ ₂ /t ₂ ×α ₂ ), can be maintained in an opposite state, and the relationship between the electrodes is The ratio of resistance to temperature change cancels out. In the above formula (1), |ρ ₁ /t ₁ ×α ₁ +ρ ₂ /t ₂ ×α ₂ | is (2×min(|ρ ₁ /t ₁ ×α ₁ |,|ρ ₂ /t ₂ ×α By making ₂ |)) small, fluctuations in the output due to temperature changes of the first electrode 20 and the second electrode 40 can be suppressed.

That is, the ratio of the resistance of the first electrode 20 to the temperature change (ρ ₂ /t ₂ ×α ₂ ) and the ratio of the resistance of the second electrode 40 to the temperature change (ρ ₂ /t ₂ × α ₂ ) The absolute value of the average sum is the ratio of the resistance of the first electrode 20 to the temperature change (ρ ₂ /t ₂ ×α ₂ ) and the ratio of the resistance of the second electrode 40 to the temperature change (ρ ₂ /t ₂ ×α ₂ ), fluctuations in the output due to temperature changes of the first electrode 20 and the second electrode 40 can be sufficiently suppressed.

The method for manufacturing the sensor device 1A is not particularly limited, and any manufacturing method can be used as appropriate. An example of a method for manufacturing the sensor device 1A will be described.

First, the first electrode 20 is deposited (formed) on the upper surface of the flexible base material 10 formed to a predetermined size.

The method for forming the first electrode 20 is not particularly limited, and may be either a dry process or a wet process. If a dry process is used as a method for forming the first electrode 20, the thin first electrode 20 can be easily formed. Examples of the dry process include sputtering and vapor deposition, and examples of the wet process include plating. As the sputtering, for example, a DC (direct current) or RF (high frequency) magnetron sputtering method can be used. By using sputtering as a method for forming the first electrode 20, the first electrode 20 with high density and thinness can be easily formed. Therefore, sputtering is preferable as a method for forming the first electrode 20. As the first electrode 20, for example, an ITO film, an IZO film, a Ti film, or the like formed by DC (direct current) or RF (radio frequency) magnetron sputtering method can be used.

The first electrode 20 may be formed on the entire upper surface of the flexible base material 10. Further, the first electrode 20 may be formed into a suitably arbitrary shape by processing it into a pattern having a predetermined shape by etching or the like. For example, the first electrodes 20 may be patterned into stripes, and a plurality of them may be arranged in stripes.

Next, a piezoelectric layer 30 is formed on the upper surface of the first electrode 20. For example, a film is formed by DC magnetron sputtering in a mixed gas atmosphere containing an inert gas such as Ar and a trace amount of oxygen using a target containing elements constituting the piezoelectric material. A piezoelectric layer 30 is formed by sputtering a piezoelectric material onto the first electrode 20 .

When the piezoelectric material is a wurtzite crystal material made of ZnO, a ZnO sintered target can be used as the target. A ZnO sintered target is installed in a sputtering device, and a mixed gas containing oxygen and an inert gas such as Ar atoms is supplied into the sputtering device. By sputtering using a ZnO sintered target in a mixed gas atmosphere containing an inert gas and oxygen, the amount of inert gas that enters the ZnO film on the first electrode 20 is suppressed, and A piezoelectric layer 30 can be obtained.

When the piezoelectric material is a wurtzite crystal material made of Mg-added ZnO containing ZnO and MgO in a predetermined mass ratio, a multidimensional sputtering method using a target made of a ZnO sintered body and a target made of an MgO sintered body, Alternatively, a one-shot sputtering method using an alloy target containing ZnO and MgO, such as a ZnO sintered target to which MgO is added in advance at a predetermined ratio, can be used.

When using the multi-source sputtering method, a multi-source sputtering device is used to supply a mixed gas containing an inert gas such as Ar atoms and oxygen into the multi-source sputtering device. The first electrode 20 is sputtered simultaneously and independently using a ZnO sintered target and an MgO sintered target in a mixed gas atmosphere containing an inert gas and oxygen. A piezoelectric layer 30 made of Mg-doped ZnO can be formed thereon. Further, at this time, Mg-doped ZnO can be formed while suppressing the amount of inert gas that enters during the formation of Mg-doped ZnO.

When using the one-source sputtering method, sputtering is performed in a mixed gas atmosphere containing oxygen and an inert gas such as Ar atoms using, for example, a ZnO sintered target to which MgO has been added at a predetermined ratio. A piezoelectric layer 30 made of a Mg-doped ZnO thin film can be formed on the electrode 20 of the first embodiment. Further, at this time, the film may be formed so that the inert gas is included in the Mg-added ZnO in a desired proportion. As a result, a piezoelectric layer 30 containing a desired amount of inert gas in Mg-doped ZnO is obtained.

In the mixed gas atmosphere containing an inert gas and oxygen, the ratio of the flow rate of oxygen to the total flow rate of the inert gas and oxygen is preferably 5% to 15%. If the ratio of the flow rate of oxygen to the total flow rate of inert gas and oxygen is within the above preferable range, when forming the piezoelectric layer 30 by sputtering using a target containing an inert gas, Ar atoms, etc. Even if an inert gas enters into the crystal lattice of a wurtzite crystal material such as ZnO, the amount of inert gas that enters can be suppressed. Therefore, the piezoelectric properties of the piezoelectric material can be improved.

The pressure in the mixed gas atmosphere during sputtering is preferably 0.1 Pa to 2.0 Pa. If the pressure is within the above preferred range, when forming the piezoelectric layer 30 by sputtering using a target containing a positive element constituting a wurtzite crystal material such as Zn, an inert gas such as Ar atoms may be used. It is possible to suppress the amount of ZnO that enters the crystal lattice of a wurtzite crystal material such as ZnO. Therefore, the piezoelectric properties of the piezoelectric layer 30 can be improved.

The film-forming temperature of the piezoelectric layer 30 is not particularly limited, and can be appropriately selected depending on the layer structure of the sensor device 1A. For example, the piezoelectric layer 30 may be formed at 150° C. or lower.

By using a sputtering method to form the first electrode 20 and the piezoelectric layer 30, a uniform film with strong adhesion can be formed while maintaining the composition ratio of the compound target. In addition, the first electrode 20 and piezoelectric layer 30 having a desired thickness can be formed with high precision only by controlling the time.

Note that the piezoelectric layer 30 may be configured by laminating a plurality of layers.

Next, a second electrode 40 having a predetermined shape is formed on the top surface of the piezoelectric layer 30.

The second electrode 40 can be formed using the same formation method as the first electrode 20.

The thickness of the second electrode 40 can be designed as appropriate, and may be, for example, 20 nm to 100 nm.

The second electrode 40 may be formed on the entire surface of the piezoelectric layer 30, or may be formed in any suitable shape. For example, when the first electrode 20 is formed in a stripe shape, the second electrode 40 is formed in a direction perpendicular to the direction in which the stripes of the first electrode 20 extend in a plan view of the sensor device 1A. A plurality of stripes may be formed.

By forming the second electrode 40 on the piezoelectric layer 30, the sensor device 1A is formed.

Note that after forming the second electrode 40, the entire sensor device 1A may be heat-treated at a temperature lower than the melting point or glass transition point of the flexible base material 10 (for example, 130° C.). By this heat treatment, the first electrode 20 and the second electrode 40 can be crystallized and their resistance can be lowered. The heat treatment is not essential, and may not be performed after the sensor device 1A is formed, such as when the flexible base material 10 is made of a material that does not have heat resistance.

In this way, the sensor device 1A according to the present embodiment includes the flexible base material 10, the first electrode 20, the piezoelectric layer 30, and the second electrode 40, and the first electrode 20 has a positive value and The second electrode 40 has a TCR of one of the negative values, and the second electrode 40 has the TCR of the other of the positive and negative values. Thereby, the sensor device 1A can cancel out the resistance change due to the temperature change of the first electrode 20 and the resistance change due to the temperature change of the second electrode 40. Specifically, the sensor device 1A calculates the absolute value of the average of the ratio of the resistance of the first electrode 20 to the temperature change and the ratio of the resistance of the second electrode 40 to the temperature change. The ratio of the resistance of the second electrode 40 to the temperature change and the ratio of the resistance of the second electrode 40 to the temperature change, whichever is smaller, can be suppressed. The sensor device 1A cancels the resistance change of the first electrode 20 and the second electrode 40 caused by the temperature change of the environment in which it is used. Fluctuations in voltage drop can be suppressed.

The sensor device 1A allows the piezoelectric layer 30 to stably exhibit high piezoelectric efficiency in the thickness direction by suppressing fluctuations in the voltage drop of the first electrode 20 and the second electrode 40 due to temperature changes. Excellent piezoelectric properties can be maintained. Therefore, the sensor device 1A can maintain excellent piezoelectric properties.

In the sensor device 1A, the first electrode 20 and the second electrode 40 can be arranged to face each other with the piezoelectric layer 30 in between. The sensor device 1A is configured by arranging a first electrode 20 and a second electrode 40 on a flexible base material 10 so as to face each other in a plane direction or a height direction with a piezoelectric layer 30 in between. However, the resistance change caused by the temperature change of the first electrode 20 and the second electrode 40 can be canceled out. Therefore, even when the sensor device 1A is used for various purposes, it is possible to suppress fluctuations in the voltage drop of the first electrode 20 and the second electrode 40 caused by changes in the temperature of the environment in which the sensor device 1A is used.

The sensor device 1A has a first electrode 20 and a second electrode 40 arranged to face each other, and a flexible base material 10, a first electrode 20, a piezoelectric layer 30, and a second electrode 40. It can be provided by laminating in this order from the flexible base material 10 side. Even if the sensor device 1A is configured by laminating the flexible base material 10, the first electrode 20, the piezoelectric layer 30, and the second electrode 40, the temperature of the first electrode 20 and the second electrode 40 remains constant. Since the resistance changes accompanying the changes can be canceled out, it is possible to suppress fluctuations in the voltage drops of the first electrode 20 and the second electrode 40 caused by changes in the temperature of the environment in which they are used.

The sensor device 1A can use the flexible base material 10 as a support. The sensor device 1A cancels out resistance changes due to temperature changes in the first electrode 20 and the second electrode 40 even when the first electrode 20 and the second electrode 40 are installed on a highly flexible substrate. Therefore, it is possible to suppress fluctuations in the voltage drop of the first electrode 20 and the second electrode 40 caused by temperature changes in the environment in which the electrode is used.

The sensor device 1A can use the piezoelectric layer 30 as a functional layer. Even if the sensor device 1A uses the piezoelectric layer 30 as a functional layer, the resistance change caused by the temperature change of the first electrode 20 and the second electrode 40 can be canceled out. Fluctuations in voltage drop between the first electrode 20 and the second electrode 40 caused by this can be suppressed. Therefore, the sensor device 1A can exhibit excellent piezoelectric properties as a piezoelectric device.

In the sensor device 1A, since the piezoelectric layer 30 can contain an inorganic material, the sensor device 1A can be used as a piezoelectric device even if the piezoelectric layer 30 is made of various inorganic materials depending on the intended use. Functions can be demonstrated stably.

The sensor device 1A can suppress fluctuations in the voltage drop of the first electrode 20 and the second electrode 40 due to temperature changes in the environment in which it is used, and can maintain excellent piezoelectric properties, so it can be suitably used as a piezoelectric device. can. Examples of piezoelectric devices include devices that utilize piezoelectric effects such as force sensors for touch panels, pressure sensors, acceleration sensors, angular velocity sensors, and acoustic emission (AE) sensors; speakers that utilize inverse piezoelectric effects; transducers; and high-frequency filter devices. , piezoelectric actuators, optical scanners, heads for inkjet printers, MEMS mirrors for scanners, and the like.

In addition, in this embodiment, the sensor device 1A is not limited to the above configuration, and is used by connecting the first electrode 20 and the second electrode 40 on the flexible base material 10 via a functional layer. Other configurations may be used as long as fluctuations in the voltage drop of the first electrode 20 and the second electrode 40 caused by changes in the temperature of the environment can be suppressed. For example, as shown in FIG. 3, the sensor device 1B includes a functional layer 50A arranged on the upper surface of the flexible base material 10, and a first electrode 20 and a second electrode 40 arranged on the upper surface of the functional layer 50A. The first electrode 20 and the second electrode 40 may be horizontally opposed to each other on the upper surface of the functional layer 50A. Further, the first electrode 20 and the second electrode 40 may be formed in a comb-teeth shape so that parts of these electrodes are interlocked with each other alternately on the upper surface of the functional layer 50A. The sensor device 1B shown in FIG. 3 can be made to function as a temperature sensor by, for example, making the functional layer 50A function as a temperature measurement layer.

In this embodiment, as shown in FIG. 4, the sensor device 1C has a meandering structure such that the first electrode 20 and the second electrode 40 are horizontally opposed to each other on the upper surface of the flexible base material 10. They may be arranged so as to be connected via the formed functional layer 50B. The first electrode 20 and the second electrode 40 may be formed in a line shape. The sensor device 1C shown in FIG. 4 can also be made to function as a temperature sensor by, for example, making the functional layer 50B function as a temperature measurement layer.

In this embodiment, the sensor device 1A may include a single layer or two or more insulating layers between the piezoelectric layer 30 and the second electrode 40. The insulating layer may be formed on the entire top surface of the piezoelectric layer 30.

Insulating materials forming the insulating layer include metal oxides such as silicon oxide (SiOx), aluminum oxide (AlOx), tantalum oxide (TaOx), yttrium oxide (YOx), zirconium oxide (ZrOx), and hafnium oxide (HfOx). , nitrides such as silicon nitride (SiNx) and silicon oxynitride (SiON), polypropylene (PP), polycarbonate (PC), ABS resin, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), poly Examples include organic insulating materials such as methyl methacrylate (PMMA), polyvinyl alcohol (PVA), and polyvinylphenol (PVP). These may be used alone or in combination of two or more.

Hereinafter, the embodiments will be described in more detail with reference to Examples and Comparative Examples, but the embodiments are not limited to these Examples and Comparative Examples.

<Example 1>
[Preparation of sensor device]
1. Fabrication of the first electrode Zn and In were adjusted to a composition ratio of 9:1 on the base material (PET, thickness: 50 μm) by DC magnetron sputtering in a mixed gas atmosphere of Ar and O ₂ Using the prepared sputtering target, a first amorphous IZO (ZnO:In ₂ O ₃ = 9:1) film in which the composition ratio of ZnO and In ₂ O ₃ was adjusted to 9:1 was formed. A film was formed as an electrode. The thickness of the IZO film was 100 nm.

2. Preparation of functional layer (piezoelectric layer) A ZnO thin film having a hexagonal wurtzite structure was formed on the IZO film by DC sputtering in a mixed gas atmosphere of Ar and O ₂ using a ZnO sputtering target. was fabricated as a piezoelectric layer which is a functional layer. The thickness of the ZnO thin film was 500 nm.

3. Preparation of Second Electrode A Ni film was formed as a second electrode on the ZnO thin film by DC magnetron sputtering in an Ar gas atmosphere using a Ni sputtering target. The thickness of the Ni film was 50 nm.

Thereby, a laminate in which the first electrode, the functional layer, and the second electrode were laminated in this order on the base material was manufactured as a sensor device. Table 1 shows the configurations of the first electrode, functional layer, and second electrode.

[Evaluation of cancellation of resistance change due to temperature change of first electrode and second electrode]
From the left side of the following formula (1), find the "absolute value of the average of the sum of the ratio of the resistance of the first electrode to the temperature change and the ratio of the resistance of the second electrode to the temperature change", and use the following formula (1). From the right side of , "twice the smaller value of the ratio of the resistance of the first electrode to the temperature change and the ratio of the resistance of the second electrode to the temperature change" was calculated. If the right side of equation (1) below is larger than the left side of equation (1) below, the resistance change due to temperature change of the first electrode and the resistance change due to temperature change of the second electrode cancel each other out. It was possible to suppress fluctuations in the voltage drop of the first electrode and the second electrode caused by temperature changes in the environment in which it is used, and was evaluated as good.
|ρ ₁ /t ₁ ×α ₁ +ρ ₂ /t ₂ ×α ₂ |<2×min(|ρ ₁ /t ₁ ×α ₁ |,|ρ ₂ /t ₂ ×α ₂ |) ... (1 )

[Example 2]
[Preparation of sensor device]
1. Fabrication of the first electrode After forming a Cu film by DC magnetron sputtering in an Ar atmosphere on a rectangular base material (PET, thickness: 50 μm), etching is performed to form a line near one end of the base material. A first electrode formed in a shape was manufactured.

2. Preparation of functional layer (temperature sensing layer) After forming a Ni film on the base material by DC magnetron sputtering in an Ar atmosphere, etching is performed to form a meandering line, one end of which is the first electrode. A functional layer formed to be connected to was produced.

3. Fabrication of the second electrode After forming a CrNi film on the base material by DC magnetron sputtering in an Ar and N ₂ mixed gas atmosphere, etching is performed to form the end of the base material opposite to the first electrode side. A second electrode formed in a line shape so as to face the first electrode was prepared nearby.

As a result, the first electrode and the second electrode are arranged to face each other in the horizontal direction on the base material, and the electrodes are connected to each other via the meandering functional layer. A sensor device was manufactured using the following methods. Table 1 shows the configurations of the first electrode, functional layer, and second electrode, and the calculation results of the left and right sides of equation (1) above.

[Comparative example 1]
In Example 1, the same method as in Example 1 was conducted except that the configurations of the first electrode, functional layer, and second electrode were changed to those shown in Table 1. Table 1 shows the configurations of the first electrode, functional layer, and second electrode, and the calculation results of the left and right sides of equation (1) above.

[Comparative example 2]
In Example 2, the same method as in Example 2 was carried out except that the configurations of the first electrode, functional layer, and second electrode were changed to the configurations shown in Table 1. Table 1 shows the configurations of the first electrode, functional layer, and second electrode, and the calculation results of the left and right sides of equation (1) above.

From Table 1, in Examples 1 and 2, of the TCR of the first electrode and the TCR of the second electrode, the TCR of one electrode is set to a positive value, and the TCR of the other electrode is set to a negative value. It was confirmed that the right side of the above equation (1) was larger than the left side of the above equation (1). That is, in Examples 1 and 2, the ratio of the resistance of the first electrode to the temperature change (ρ ₂ /t ₂ × α ₂ ) and the ratio of the resistance of the second electrode to the temperature change (ρ ₂ /t ₂ × α 2 ) α ₂ ), the ratio of the resistance of the first electrode to the temperature change (ρ ₂ /t ₂ × α ₂ ) and the ratio of the resistance of the second electrode to the temperature change (ρ ₂ /t ₂ ×α ₂ ).

On the other hand, in Comparative Examples 1 and 2, both the TCR of the first electrode and the TCR of the second electrode are set to positive values or negative values, so that the left side and right side of the above equation (1) become the same. It was confirmed that That is, in Comparative Examples 1 and 2, the ratio of the resistance of the first electrode to the temperature change (ρ ₂ /t ₂ × α ₂ ) and the ratio of the resistance of the second electrode to the temperature change (ρ ₂ /t _{2 × α 2} ) α ₂ ), the ratio of the resistance of the first electrode to the temperature change (ρ ₂ /t ₂ ×α ₂ ) and the ratio of the resistance of the second electrode to the temperature change (ρ ₂ /t ₂ × α ₂ ).

Therefore, in Examples 1 and 2, unlike Comparative Examples 1 and 2, by setting the TCR of the first electrode and the TCR of the second electrode to different signs, changes in the temperature of the first electrode can be suppressed. Since the accompanying resistance change and the resistance change due to the temperature change of the second electrode can be offset, it can be said that fluctuations in the voltage drop of the electrode of the sensor device caused by the temperature change of the environment in which the sensor device is used can be suppressed.

Although the embodiments have been described as above, the embodiments are presented as examples, and the present invention is not limited to the embodiments described above. The embodiments described above can be implemented in various other forms, and various combinations, omissions, substitutions, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

Note that aspects of the embodiment of the present invention are, for example, as follows.
<1> A functional layer and a pair of electrodes connected in series via the functional layer are provided on a support,
The pair of electrodes includes a first electrode having a temperature coefficient of resistance of one of a positive value and a negative value, and a second electrode having a temperature coefficient of resistance of the other value of a positive value and a negative value. A sensor device consisting of an electrode.
<2> The sensor device according to <1>, wherein the first electrode and the second electrode are arranged to face each other.
<3> The first electrode is provided on the support side surface of the functional layer,
The second electrode is provided on a side of the functional layer that is different from the support side,
The sensor device according to <1> or <2>, wherein the support, the first electrode, the functional layer, and the second electrode are stacked in this order.
<4> The sensor device according to any one of <1> to <3>, wherein the support is a flexible base material.
<5> The sensor device according to any one of <1> to <4>, wherein the functional layer is a piezoelectric layer.
<6> The sensor device according to <5>, wherein the piezoelectric layer contains an inorganic material.

This application claims priority based on Japanese Patent Application No. 2022-037075 filed with the Japan Patent Office on March 10, 2022, and all contents described in said application are incorporated.

1A, 1B, 1C sensor device 10 flexible base material 20 first electrode 30 piezoelectric layer 40 second electrode 50A, 50B functional layer

Claims (6)

A functional layer and a pair of electrodes connected in series via the functional layer are provided on the support,
The pair of electrodes includes a first electrode having a temperature coefficient of resistance of one of a positive value and a negative value, and a second electrode having a temperature coefficient of resistance of the other value of a positive value and a negative value. A sensor device consisting of an electrode. The sensor device according to claim 1, wherein the first electrode and the second electrode are arranged to face each other. the first electrode is provided on the surface of the functional layer on the support side,
The second electrode is provided on a side of the functional layer that is different from the support side,
The sensor device according to claim 2, wherein the support, the first electrode, the functional layer, and the second electrode are stacked in this order. The sensor device according to claim 1, wherein the support is a flexible base material. The sensor device according to claim 1, wherein the functional layer is a piezoelectric layer. The sensor device according to claim 5, wherein the piezoelectric layer contains an inorganic material.

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